Abstract

We demonstrate spatial control of optical near-fields by femtosecond phase shaping in one-dimensional plasmonic structures. The near-field images display striking temporal-phase dependence, switching between double- and single-peak images within one lattice constant. The change of the near-field distribution is studied in the time and spectral domain. The spectral composition change observed by varying the time delay between two phase-locked femtosecond pulses explains the spatial control of the near-field images. Modal expansion calculations of linear light transmission using the surface impedance boundary condition are in excellent agreement with experiments.

Figures (5)

(a). Scanning electron microscope image of the nanoslit array. (b) Near-field transmission images of the nanoslit array excited by monochromatic light with a wavelength of 780 nm (top) and 840 nm (bottom). The slit positions are depicted as black dashed lines in (b). (c) Cross sections of (b) showing the double periodic and the single periodic pattern within one lattice constant for excitation wavelengths of 780 nm (top) and 840 nm(bottom).

(a). Phase control of spatial near field distributions by coherently controlled femtosecond pulse pairs (schematic). Near field transmission images recorded for excited by the two pulses of time delay τ=13.0 fs with (b) Δϕ=0, (c) Δϕ=-π, respectively. The slit positions are depicted as black dashed lines in (b) and (c).

Cross section intensities of Fig. 2(b), (c) (black solid lines) and theoretical simulations (red dashed lines) from the diffraction order expansion together with SIBC considering the phase-controlled variation of the pulse spectrum with time delay τ=13.0 fs (top for Δϕ=0, bottom for Δϕ=-π).